JPH0565254B2 - - Google Patents

Description

[Detailed description of the invention]

A. Purpose of the invention (1) Industrial field of application The present invention relates to a stove cap for an internal combustion engine, particularly a pair of flat joint surfaces joined to the large end face of the stove main body, and an intermediate between the two joint surfaces. The present invention relates to a method for manufacturing a stove cap having a bearing surface having a semicircular cross section and forming a crankshaft bearing hole between the shaft cap and the end surface. (2) Conventional technology Conventionally, the stove caps mentioned above have been manufactured by casting or forging. (3) Problems to be Solved by the Invention However, since casting defects cannot be avoided in the manufacture of cast products, a large safety factor is taken in anticipation of such defects, which increases weight and limits miniaturization. In the case of a cast stove cap, it cannot be applied to a small, lightweight, high-output internal combustion engine, and it has been difficult to accurately form the bearing surface and joint surface of the stove rod cap by casting. On the other hand, forged products are manufactured by forging a rod-shaped material obtained by extrusion processing, so the yield of the material is poor due to the generation of burrs during the forging process, and the processing cost is also high. This results in an increase in manufacturing costs. In view of the above, an object of the present invention is to provide a method for manufacturing a conrod cap for an internal combustion engine, which is lightweight and can provide a conrod cap having excellent fatigue strength and wear resistance at a low cost. B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides a pair of flat joint surfaces to be joined to the end surface on the large end side of the cooking rod main body, and an intermediate between the two joint surfaces. A method for producing a stove cap for an internal combustion engine, which has a bearing surface having a semicircular cross section and forming a crankshaft bearing hole between the end surface and the end surface, the A step of sequentially performing treatment and hot extrusion to obtain a stove cap material made of a sintered body, and cutting the stove cap material along a plane perpendicular to the extrusion direction to form a plurality of stove caps. and the extrusion direction is set to be parallel to the axis of the bearing surface. (2) Effect The grain size of the structure on the outer periphery of the conrod cap, including the bearing surface, is made finer than the grain size of the inner structure due to frictional contact with the inner wall of the die hole during extrusion processing. On the other hand, since the flow direction of the tissue at the outer periphery is aligned parallel to the axis of the bearing surface, the outer periphery including the bearing surface, where the load stress is highest in the conrod cap, is densely distributed over the entire area in the axial direction of the bearing surface. As a result, the fatigue strength of the entire outer peripheral portion including the bearing surface is significantly improved, and the wear resistance of the bearing surface is uniformly improved over the entire axial direction. In addition, the pair of joint surfaces with the large end side of the stove rod main body, which require relatively high processing accuracy on the outer periphery of the stove cap, can be precisely formed at the same time as the bearing surface during the extrusion process,
Moreover, by simply cutting the stove cap material along a plane perpendicular to the axis, a plurality of stove rod caps having the same cross section can be obtained, making mass production easy. In addition, the extrusion direction of the stove cap is parallel to the axis of the bearing surface, resulting in a good weight balance in the axial direction.Furthermore, due to the extrusion process, the cap is symmetrical with respect to the vertical axis of the stove. Even objects with complex cross-sectional shapes can be formed with high precision. (3) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, in FIG. It consists of a stove top cap 1 joined to an end face 2l, and the stove rod body 2 and the stove top cap 1 are removably connected by bolts 3. A bearing hole 4 for a piston pin is bored in the small end of the conrod main body 2, and a bearing hole for a crankshaft is formed in the end face 2l on the large end side in cooperation with the conrod cap 1. A bearing recess 5 is formed for this purpose. FIG. 2 shows a condensing rod cap 1 for an internal combustion engine obtained by the method of the present invention, and on the surface facing the conrod main body 2, there is a pair of caps joined to the end surface 2l on the large end side of the conrod main body 2. flat joint surface 1
b, 1b, and a bearing surface 1a having a semicircular cross section and forming a crankshaft bearing hole between the bearing recess 5 and the bearing surface 1a, which is located between the joint surfaces 1b, 1b. The surfaces 1b and 1a are formed parallel to the extrusion direction P of the stove cap material M, that is, parallel to the axis O--O, as will be described later. Next, the method for manufacturing the stove cap 1 will be explained. The method includes a step of compacting a billet from aluminum or aluminum alloy powder, a step of subjecting the compacted billet to heat treatment, and a step of compacting the billet from aluminum or aluminum alloy powder. A step of obtaining a stove cap material M (FIG. 3) made of a sintered body by hot extrusion processing from In the extrusion step, the extrusion direction P of the billet is set to be parallel to the axis OO of the bearing surface 1a. To explain a specific example of the above manufacturing method, the aluminum alloy used in carrying out the method of the present invention preferably contains chemical components in the following range. 12.0wt%≦Si≦28.0wt% 0.8wt%≦Cu≦5.0wt% 0.3wt%≦Mg≦3.5wt% 2.0wt%≦Fe≦10.0wt% 0.5wt%≦Mn≦5.0wt% Si is It has the effect of improving abrasion resistance, Young's modulus, strength and thermal conductivity, and lowering the coefficient of thermal expansion. However, when the Si content is less than 12.0% by weight, the wear resistance and strength decrease;
If it exceeds this, the formability in hot extrusion processing will deteriorate, leading to a decrease in mass productivity. Cu has the effect of strengthening the Al matrix through heat treatment. However, the Cu content is 0.8% by weight.
If it is less than 5.0% by weight, the above effect cannot be obtained;
If it exceeds , the formability in hot extrusion and stress corrosion cracking resistance will deteriorate. Like Cu, Mg has the effect of strengthening the Al matrix through heat treatment. However, if the Mg content is less than 0.3% by weight, the above effects cannot be obtained, while if it exceeds 3.5% by weight, the formability in hot extrusion and stress corrosion cracking resistance deteriorate. Fe has the effect of improving high temperature strength and Young's modulus. However, if the Fe content is less than 2.0% by weight, no improvement in high temperature strength can be expected;
If it exceeds % by weight, molding in hot extrusion becomes impossible. Mn is an important chemical component, and has the effect of improving high temperature strength and stress corrosion cracking resistance, and improving formability in hot extrusion processing, especially in the range of Fe≧4% by weight. However, if the Mn content is less than 0.5% by weight, the above effects cannot be obtained,
On the other hand, if it exceeds 5.0% by weight, the moldability will deteriorate. For example, an air atomization method is applied to manufacture the aluminum alloy powder. Further, as the powder compacting method, a cold isostatic pressing method (CIP method) or a mold compression molding method is applied. Further, the extrusion process is performed hot, and both direct extrusion (front extrusion) and indirect extrusion (backward extrusion) are applicable. The table shows the composition of the aluminum alloy used in the present invention and the aluminum alloy used in the comparative example.

[Table] (a) Using the aluminum alloy shown in the table, air atomization was applied to produce powder at a cooling rate of 10 ² to ^{10 4} °C/sec, and the powder was classified to a particle size smaller than 100 mesh. obtained alloy powder. In this case, if the cooling rate is less than 10 ² °C/sec, coarse Al-Si-Fe intermetallic compounds will crystallize and cause the above-mentioned problems, so it is necessary to strictly adhere to the cooling rate. (b) Using each alloy powder, cold isostatic pressing or die compression molding is applied to compact a round billet for extrusion with a density ratio of 75% and a diameter of 225 mm. In the cold isostatic pressing method, alloy powder is placed in a rubber tube and
Molding is performed under a hydrostatic pressure of ~3.0 ton/ ^cm2 , and in the mold compression molding method, alloy powder is placed in the mold and molded under a pressure of 1.5-3.0 ton/ ^cm2 in the air at room temperature. conduct. (c) Place each billet in a soaking furnace with an internal temperature of 500°C and hold for 4 hours to heat-treat each billet. (d) Each billet is extruded at a billet temperature of 380°C and an extrusion ratio of 28 to form a stove cap material M shown in FIG. The extrusion direction P of this material M is the bearing surface 1.
It is extruded parallel to the axis O-O of a,
In the illustrated example, it is cut at two equal positions in the direction of the axis O--O, that is, at the positions indicated by the chain lines in FIG. 3, to obtain two stove caps 1, 1. (e) For each material 1, heat at 490℃ for 2 hours, cool with water,
and T6 treatment consisting of heating at 175°C for 8 hours. (f) Mechanically divide each material 1 into two equal parts as described above,
They are machined and finished to obtain stove caps 1,1. For comparison, a casting material was melted using the aluminum alloy shown in the table above, and the material was subjected to casting processing to obtain a stove cap. In this stove cap, the flow direction of the fibrous structure is perpendicular to the center line of the bearing surface due to the direction of pressurization. Also, a stove cap is obtained by casting using the aluminum alloy shown in the table above. No fibrous tissue occurs in this stove cap. Bearing surface 1a in each stove cap
After polishing the cross section perpendicular to the center line O-O of
The outer periphery and internal structure of the cross section were observed using an optical microscope, and the grain size of the particles caused by the powder was determined for the stove cap according to the present invention, and the crystal grain size was determined for the comparative example. Since aluminum alloy powder has a film of Al ₂ O ₃ on its surface, it is possible to measure the particle size by determining the grain boundaries between particles using an optical microscope after hot extrusion processing. In addition, as shown in Fig. 4, for fatigue testing, each of the stove caps was assembled to the stove body type jig 02 with a pair of bolts 3, and the bearing hole 04 on the small end side and the bearing hole 04 on the big end side were assembled. Bearing installation part 05 and bearing surface 1
Round bars 6 ₁ and 6 ₂ were fitted into the bearing holes between a, respectively. The fatigue test was conducted by repeatedly applying tensile loads in opposite directions to both round bars 6 ₁ and 6 ₂ as indicated by arrow a 10 ⁷ times in an atmosphere of 200°C, and the fatigue strength The maximum tensile load at which the stove cap 1 would not break was determined. The table shows the measurement results of grain size and crystal grain size and the fatigue strength test results for each stove cap, and therefore for each alloy.

【table】

[Table] In the on-rod cap 1 obtained by the method of the present invention, the grain size of the structure of the outer peripheral part including the bearing surface 1a is changed due to frictional contact with the inner wall of the die hole during the extrusion process. The grain size is much finer than that of the inner structure, and the flow direction of the structure at the outer periphery of the cap is aligned parallel to the axis O-O, so the load stress is highest in the stove cap 1. Since the outer peripheral part including the bearing surface 1a can be made into a dense and uniform layer over the entire area in the direction of the axis O-O, the fatigue strength of the entire outer peripheral part including the bearing surface 1a is significantly improved. The wear resistance of the bearing surface 1a is uniformly improved throughout its axial direction. As a result, as shown in the table, the conrod cap according to the present invention has improved fatigue strength compared to the one in the table. As mentioned above, the grain size of the outer periphery of the stove cap according to the present invention is refined due to the frictional contact of the outer periphery with the extrusion die, but at the same time, the eutectic Si is spheroidized due to frictional heat. As the cracking progresses, the notch fatigue strength of the stove cap can be particularly improved. The optimum range is that the maximum particle size at the outer periphery is 100 μm or less, and the maximum particle size inside is 150 μm or less.
If the maximum particle size on the outer periphery exceeds 100μm, the effect of extrusion processing will be small, and the maximum particle size on the inside will decrease.
When the thickness exceeds 150 μm, fatigue strength decreases. In order to set the particle size of the outer peripheral part and the inside as described above, it is sufficient to use the aluminum alloy powder whose particle size is smaller than 100 mesh. Incidentally, it is also possible to use aluminum powder in the stove cap of the present invention. C. Effects of the Invention As described above, according to the present invention, the step of sequentially subjecting aluminum or aluminum alloy powder to powder compaction, heat treatment, and hot extrusion processing to obtain a stove cap material made of a sintered body; the step of cutting the stove cap material along a plane perpendicular to the extrusion direction to obtain a plurality of stove caps, and the extrusion direction is set to be parallel to the axis of the cap bearing surface. The grain size of the outer peripheral part of the stove cap including the bearing surface is made finer than the grain size of the inner part due to frictional contact with the inner wall of the die hole during the extrusion process. , the flow direction of the tissue at the outer circumference is aligned parallel to the axis of the bearing surface, and therefore the outer circumference including the bearing surface, where the load stress is highest in the conrod cap, is spread over the entire area in the direction of the axis of the bearing surface. Since it can be made into a dense and uniform layer throughout, the fatigue strength of the entire outer circumference including the bearing surface is significantly improved, and the wear resistance of the bearing surface is uniformly improved throughout the entire axial direction. Overall, an extremely high-performance stove cap can be obtained. In addition, the pair of joint surfaces with the large end side of the stove rod main body, which require relatively high processing accuracy on the outer periphery of the stove cap, can be precisely formed at the same time as the bearing surface during the extrusion process,
In addition, simply cutting the stove cap material along a plane perpendicular to the axis line allows multiple stove caps with the same cross section to be obtained, making mass production easy. Together with the good yield, it can greatly contribute to cost reduction. Furthermore, when cutting the stove cap material mentioned above, a stove cap of a desired thickness can be easily obtained by simply selecting the position of the cut surface appropriately, and the bearing surface of each stove cap can be easily adjusted to suit the thickness of the cap. It is advantageous that the structure can always be uniformly dense throughout the entire axial direction, regardless of the size. Furthermore, by making the extrusion direction parallel to the axial direction of the bearing surface, the stove cap has a good weight balance in the axial direction. Because it is possible to form objects with a relatively complex cross-sectional shape with left-right symmetry with high precision,
A stove cap with good weight balance as a whole can be easily obtained, and this can contribute to improving the dynamic characteristics of the stove in which the cap is incorporated.

[Brief explanation of the drawing]

Figure 1 is a side view of a stove incorporating the stove cap obtained by the method of the present invention, Figure 2 is a perspective view of the stove cap, and Figure 3 is a stove extruded according to the method of the present invention. FIGS. 4a and 4b are perspective views of the rod cap material, and show a fatigue test method for the stove cap obtained by the method of the present invention, in which a is a front view and FIG. 4b is a side view. M... Stove rod cap material obtained by extrusion processing, O-O... Straight line, 1... Stove rod cap, 1a... Bearing surface, 1b... Joint surface, 2
... Stove rod body, 2l ... End face on the large end side.

Claims (1)

[Claims] 1. A pair of flat joint surfaces 1b, 1b to be joined to the end surface 2l on the large end side of the cooking rod main body 2, and a joint located between the two joint surfaces 1b, 1b and between the end surface 2l. In a method of manufacturing a stove cap for an internal combustion engine having a bearing surface 1a having a semicircular cross section forming a bearing hole for a crankshaft, aluminum or aluminum alloy powder is sequentially subjected to powder compacting, heat treatment, and hot extrusion. and a step of cutting the stove cap material M along a plane perpendicular to the extrusion direction P to obtain a plurality of stove caps 1, 1. A method for manufacturing a stove cap for an internal combustion engine, characterized in that the extrusion direction P is set to be parallel to the axis OO of the bearing surface 1a. 2 The stove cap has a maximum grain size at the outer periphery in a cross section perpendicular to the extrusion direction.
2. The method of manufacturing a stove cap for an internal combustion engine according to claim 1, wherein the internal maximum particle diameter is set to 100 μm or less, and the maximum internal particle size is set to 150 μm or less. 3. The method of manufacturing a stove cap for an internal combustion engine according to claim 1 or 2, wherein the stove cap is made of a sintered aluminum alloy. 4 The billet used in the extrusion process is compacted using aluminum or aluminum alloy powder produced under conditions of a cooling rate of 10 ² °C/sec or higher, and the billet that has been compacted is heated at 430 °C. The method for manufacturing a stove cap for an internal combustion engine according to claim 1, 2 or 3, wherein the stove cap is subjected to a heat treatment at a temperature of 520°C or less. 5 The above-mentioned push-up process is performed at a billet temperature of 300°C or higher,
A method for manufacturing a stove cap for an internal combustion engine according to claim 1, 2, 3, or 4, which is carried out under conditions of 450° C. or lower and an extrusion ratio of 5 or more and 35 or less.